Process for the manufacture of carbon black



y 4, 1957 M. STEINSCHLAEGER 24,315

PROCESS FOR THE: MANUFACTURE OF CARBON BLACK Original Filed Oct. 12. 1948 2 Sheets-Sheet 1 y 1957 M. STEINSCHLAEGER Re. 24,315

PROCESS FOR THE MANUFACTURE OF CARBON BLACK Original Filed Oct. 12. 1948 2 Sheets-Sheet 2 F l G .2 a9

In veafir I Max/4:4 ri/nf/sa/zaife United States Patent PROCESS FOR THE MANUFACTURE OF CARBON BLACK Michael Steinschlaeger, London, England Original No. 2,694,621, dated November 16, 1954, Serial No. 54,090, October 12, 1948. Application for reissue April 30, 1956, Serial No. 581,817 7 Claims priority, application Great Britain October 17, 1947 11 Claims. (Cl. 23209.4)

Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to a process for the manufacture of carbon black from liquid, gaseous or solid pyrolizable carbonaceous materials, which expression as used herein means hydrocarbons, oxygen-containing derivatives of hydrocarbons, nitrogen-containing derivatives of hydrocarbons, animal or vegetable oils, fats and waxes and natural resins.

Numerous proposals have been made for the manufacture of carbon black from hydrocarbon-containing materials. The best known of them producing high grade carbon blacks are:

1. Channel black processes; 2. Furnace black processes,

(a) involving the incomplete combustion of hydrocarbon-containing material such as oil, tars, hydrocarbon gases and pitches;

(b) involving the use of hot gases obtained by the combustion of fuels [and] to crack hydrocarboncontaining material;

3. Modifications of the channel black and furnace black processes.

The processes at present in use, however, suffer from the drawback of low thermal efiiciency if a high quality carbon black is required, and also require a high capital expenditure and involve high operation and raw material costs.

My investigations have shown the reason for the low etficiency of converting carbonaceous materials into carbon black by the above processes to be as follows:

The primary reaction which takes place in the manufacture of carbon black may be expressed as follows:

(1) CnHx=I1C+XHiY cals./kgm. of carbon wherein n and x are integers and Y is the reaction heat required which varies according to the carbonaceous material used. Thus, for example, for parafiin hydrocarbons such as gas oil the reaction heat is negative and for aromatic hydrocarbons such as anthracene is positive. In addition heat is required to heat the carbonaceous material to the cracking temperature and to provide for heat losses.

Should it be possible to crack the carbonaceous material according to the primary reaction practically complete conversion of the carbon in the material used into carbon black could be efiected and a considerable proportion of hydrogen obtained.

However, it is found that according to the process used one or more secondary reactions are also proceeding in Re. 24,315 Reissued May 14, 1957 Ice addition to the main reaction (1) and these may be expressed as follows:

(2) C+CO2=2CO-3490 cals. per kgm. of carbon (3) C+H2O=CO+H22636 cals. per kgm. of carbon (4) C+2Hz=CH4+l506 cals. per kgm. of carbon (5) C+V2O=CO+2440 cals. per kgm. of carbon (6) C+O2=CO2+8O8O cals. per kgm. of carbon (7) H2+V2O2=H2O+28570 cals. per kgm. of [carbon] hydrogen Some of these reactions are required to generate the heat used for heating the carbonaceous material to the cracking temperature; to provide the heat required for the cracking reaction (if any); to provide the heat required for the other secondary reactions and, finally to provide the heat to cover the losses.

It is obvious that the secondary reactions consume according to the process in use and the quality of carbon black required a large proportion of the carbon available (e. g. in the channel process up to 9697%) and require in some processes a considerable amount of heat.

From the above it can be seen that if it were possible to suppress the whole or a part or some of the secondary reactions or to turn them to some effective use in the process, a considerably higher efficiency of the conversion could be obtained.

in addition, the quality of the carbon black would be considerably improved, because the carbon consumed in secondary reactions is the most active carbon and of very small particle size.

Reaction 2 may be suppressed by using gases free from carbon dioxide or containing only a small proportion of carbon dioxide calculated on the carbonaceous material under treatment. Thus the proportion of the carbonaceous material under treatment which is converted into carbon monoxide by reaction with carbon dioxide according to eaction 2 should be kept to a minimum, preferably not more than 10% by weight. This can be ensured either by keeping the proportion of carbon dioxide present low and/or by keeping the proportion of treatment gas to carbonaceous material low.

It has been found that besides all other side reactions the water gas reaction C+H2O=CO+H2'(3) does not occur, which can be explained, firstly, owing to the high concentration of hydrogen in the gases obtained, and, secondly, owing to the high velocity or short time of contact required to produce high quality carbon black according to the process of the present invention.

The extent to which Reaction 4 takes place depends upon the temperature of the reaction zone and the time the reaction products or reactants are in the reaction zone in the sense that the higher is the temperature the lower is the amount of methane formed and as the reaction is exothermic and only a small proportion of carbon is consumed the suppression of this reaction is not so important and in any case it increases the calorific value of the gas obtained.

Furthermore, it is obvious that Reaction 2 will take place in preference to Reactions 3 and 4 at high temperatures as the Reaction 2 requires less heat.

Reactions 5, 6 and 7 may be suppressed by using gases free from oxygen or containing only a small proportion of oxygen. But, as explained hereinafter, it is sometimes desirable to have oxygen present in the gas. but this] In this case the difiiculty can be overcome by selecting the proportion of oxygen in accordance with the proportion of hydrogen formed so that the Reactions 5 and 6 are eliminated and Reaction 7 is only disadvantageous in that it produces steam which may tend to favour Reaction 3 but this reaction may be suppressed if appropriate operating conditions are maintained as [is] explained hereinbefore. Reaction 3 may be kept to a minimum 3 byvausingashqrtztime of contact between the "gas "and 'the carbonaceous material.

While knowledge of the conditions which favor or retard or even suppress the various secondary reactions is helpful .tajhenttainment of a satisfactory cracking operation and the production of a desirable carbon black product, there still remain problems of control ,of the operating conditions and selection and regulation of the composition of the gaseous medium utilized in providing the appropriate environmentwithin -the cracking zonevif a high efficiency and a'high quality carbon black product are to be obtained.

Besidesthe control or suppressionofside reactions that tend to lower the efliciency of the cracking process there is; also the problem, when producingcarbon black by transfer of sensibleheat from very highly heated gases to the carbonaceous material'that is undergoing the cracking, of introducing .the carbonaceous material into the very hot =gases;and;quickly and uniformly bringing the temperature of the carbonaceous material to the temperature range most favorable ,for the .desired cracking reaction and at the same time subiectingrthe carbonaceous material and the resulting cracked products tothe cracking temperature only for-every short, interval of-time.

It is an-obiect of this invention more eflectively to control the secondary reactions that are necessary to provide heat required in producing the desired thermal decomposition of thecarbonaceous material and to minimize or suppress-altogether others of the secondary reactions that would tend to lower the efficiency of the conversion.

It is a further object of this invention to provide an improved process for the manufacture of carbon black of high quality andin good yield whilst overcoming the aforesaid drawbacks.

Thcprescnt invention provides a process for the manu facture of carbon black which overcomes the aforesaid drawbacks which comprises mixing a hot gas with a carbonaceous material (as hereinbefore defined) so that the .contactitime at the cracking temperature is utmost less .than five seconds and preferably less than 0.5 second, the sensible heat and the temperature of said gas being sufliciently high to heat the carbonaceous material, provide forheat lossesandcrack the carbonaceous material and the temperature :and composition of the gas andthc proportion of the gas to the carbonaceous material in conjunctiomwith the aforesaid contact time being such as to .ensure that'the cracking is effected substantially only according to the; reaction:

CnHx=nC+XHiY cals.-/kgm. of carbon :Whercin nand x'are integers and Y is the rcactionheat required.

The contact time is preferably less than 0.5 second and the cracking temperature is preferably between 800 C. and 1400" ..C., the particular temperature employed depending upon the contact time and the quality of the car- 'bon black required. Generally, the higher the cracking temperature, the shorter should be the contact time, other factors being equal.

According to onccmbodiment of the invention the hot gas is obtained by burning a fuel with an oxygen-containinggas. Preferably the fuel is a hydrogen-containing gas and a arLof the gas obtained in the :cracking is recycled and burnt to ,provide .furtherhot gas. The combustion gas preferably contains oxygen. This is effected by using an excess of oxygen or ,air inthc combustion so that when. the combustion gas is mixed in the correct proporgilOll with the carbonaceous material the hydrogcmpro' 'dHCBd by .the cracking reacts preferentially with oxygen rather/than .with the carbon whereby the output of carbonblack iszincreased. The proportionof oxygen in the ombustion ,gas may-be adjusted according to thc'hydro- .gen content of thcgcarbqnaqcousu material employed.

heating the carbonaceous material. heating may be so regulated as to influence favorably the composition of the gas leaving the reaction zone so 4 which comprises passing a[gas;'| gaseourmediumthrough a heated vessel containing checker bricks (i. e. a. regencrator) to heat the [gas] gaseous medium, mixing the [gas] gaseous medium leaving said vessel with a carbonaceous material (as hcrcinbefore defined) so that the contact time is less than live seconds, and preferably less than 0.5 second, the sensible heat and the temperature of the said-[gas] gaseous medium being sufiiciently high to heat the carbonaceous material, provide for heat losses and crack the carbonaceous-material. and the temperature and composition of the [gasllgaseous medium and the proportion of =thc [gas] gaseous medium to the carbonaceous material inaonjunction with the aforesaid contact time being such as to ensure that the cracking is effcctcd substantially ,only according to the reaction:

wherein n and x are integers and Y is the reaction heat required.

The hotIgas] gaseouszmedium leaving the vessel and .;containing hydrogen asa combustible component may be mixed with an oxygen containing gas and-the. mixture wholly or partially burnt to increase the temperature thereof be'fore mixing with the carbonaceous material. [Alternatively, the hot gas leaving the vessel may be mixed with an oxygen-containing gas and the mixture burnt -to'increase thetcmperaturc thereof before mixing with *the carbonaceous material] In fact the proportion of oxygen-containing gas [being] may be such that sufficient [heat] oxygen is present to burn part of the hydrogen formed in the cracking.

Tr'hcamixture obtained after cracking is cooled in any convenientmanner, e. g. by water, steam or cold gases. The shorter the time during which the mixture remains at a high temperature the higher will be the quality of the carbon black obtained.

The gases with the entrained carbon black are brought aftercooling directly or indirectly into an electrostatic precipitator, filtcrsor cooled by water (the cooling may be accomplished in stages) and the carbon black precipiatated.

The gases obtained in the process are [used] partly burned for heating the regenerators and partly recycled through the regcnerators to absorb heat therefrom.

When employing the second embodiment preferably two generators are provided, one being heated While the other is used, for heating the gas.

The mixing of the'hot-gascs'and the carbonaceous material may be effected in 'any convenient vessel which may be, for example, a pipe or a chamber.

In practical operation to start the plant hydrogen or steam can be used for the first cycles and then part of the gasobtained in the reaction and consisting largely of materials used ,a variable surplus is obtained which may be used .for otherpurposcs, c. g. for generation of power using gas turbines or in boilers for generation ofstcam.

The materials and gases used in the process may be prc heated if required or desirable, and may assist in this Way to increase the heat available for the reaction and for The degree of preas toassist in minimizing or entirely suppressing Reactions 2 to 7.

"The"invention'will-nowbe-further described by way of example with reference to the accompanying drawings, in which:

Fig. 1 shows diagrammatically an apparatus for carrying out the process of the invention using two regenerators,

Fig. 2 shows diagrammatically another apparatus not employing a re generator, and

Fig. 3 shows on an enlarged scale a modification of part of the apparatus of Figs. 1 and 2.

Referring to Fig. l of the drawings, the apparatus comprises two regenerators 1 and 2. The regenerator 1 contains checker bricks 3 and mounted on the top thereof is [a] an unobstructed reaction chamber 4. The regenerator 1 is provided with conduits 5 and 6, and the reaction chamber 4 is provided with conduits 7, 8, 9, 10, 11 and 12. The regenerator 2 which is similar to the regenerator 1 contains checker bricks 13 and mounted on the top thereof is [a] an unobstructed reaction chamber 14. The regenerator 2 is provided with conduits 15 and 16 and the reaction chamber 14 is provided with conduits 17, 18, 19, 20, 21 and 22. The apparatus also includes a carbon black precipitator 23 connected by a conduit 24 to conduits 9 and 19 and by a conduit 25 to a gas holder 26 having an outlet conduit 27. The conduit 27 is connected to the conduit 12 by a conduit 28 and to the conduit 22 by a conduit 29 and is also connected to the conduit 6 by a conduit 30 and to the conduit 16 by a conduit 31. It will he understood that all the conduits will be provided with control valves (not shown in the drawings). .The'regenerators 1 and 2 are alternately heated and used for heating gases and the use of the apparatus shown in Fi g. 1 will be described for the case in which regenerator 1 is being used for heating gases and regenerator 2 is being heated. Recycled gas mainly consisting of hydrogen and nitrogen is passed from the conduit 30 through the conduit 6 into the heated regenerator 1 and the heated gas passed into the reaction chamber 4 where it is partially burnt by means of air admitted through conduit 11 so that its temperature is increased whereafter it meets hydrocarbomcontaining material, preferably a hydrocarbon oil or gas introduced through the conduit 7. Instead of introducing the hydrocarbon gas or oil through the conduit 7 directly into the reaction chamber, it is advantageous to substitute for the pipe 7 the mixing apparatus shown in Fig. 3 and more particularly hereinafter described. The hydrocarbon-containing material is cracked and the products obtained are cooled by gas admitted through conduit 10 and the products then leave the reaction chamber through conduit 9 and pass through conduit 24 to the carbon black precipitator 23 where carbon black is separated and the gaseous products mainly consisting of hydrogen and nitrogen pass into conduit 27 where part is passed via conduit 10 to be used as cooling gas for the reaction chamber 4. Another part is recycled via conduit 30 and a third part is passed through conduit 29 to conduit 22 to be used as gas for burning to heat the regenerator 2. Simultaneously with the production of carbon black in reaction chamber 4 as above described, regenerator 2 is being heated as follows: Air is admitted through conduit 18 and gas or oil for burning as fuel through conduit 22 supplemented by recycled gas supplied through conduit 29. The hot gas produced heats the checker brickwork 13 and the waste gases leave through conduit 15. The air burns any carbon deposited in reaction chamber 14 from a previous operation. In starting up the apparatus, gas to be heated may be supplied from outside the system through tonduit 5. It will be understood that after the cycle described above the roles of the regenerators are reversed and in the next cycle r'egenerator 1 is heated and regenerator 2 is used for heating gases.

Referring to Fig. 2 of the drawings, the apparatus comprises [a] an unobstructed reaction chamber 32 connected by aconduit 33 to a carbon black precipitator 34 which in turn is connected by a conduit 35 to a gas holder nected thereto to form gas burners.

36 which has an outlet conduit 37. The conduit 37 has branch conduits 38, 39, 40 and 41, the last three of which have air supply conduits 42, 43 and 44 respectively con- Conduits 45 and 46 are provided for the introduction of hydrocarbon-containing material to be cracked. In addition a conduit 47 is provided for the admission of water or steam for cooling. It will be understood that all the conduits will be provided with control valves (not shown in the drawings).

In operation hot gas is produced by burning recycled gas mainly consisting of hydrogen and nitrogen supplied through conduits 39, 40 and 41 by air admitted through conduits 42, 43 and 44. The hot gas thus produced proceeds down the reaction chamber 32 and meets hydrocarbon-containing material, preferably a hydrocarbon oil or gas, admitted through conduits 45 and 46. The hydrocarbon-containing material is cracked and the products leave through conduit 33. They are cooled first by gas admitted through conduit 38 and then by water or steam admitted through conduit [44] 47 and the carbon black is separated in the carbon black separator 34. The gases mainly consisting of hydrogen and nitrogen pass into the gas holder 36 and leave through outlet conduit 37 whence a part is recycled through conduits 39, 40 and 41 and a part is used for cooling the reaction products by introduction through conduit 38 into the reaction chamber 32.

To overcome the difiiculty of introducing hydrocarboncontaining material into very hot gases the apparatus for effecting this mixture may take the form shown in Fig. 3 of the drawings. Referring to Fig. 3 of the drawings, the mixing apparatus comprises a burner 48 having a gas conduit 49 and air conduit 50. This burner leads into a tube 51 lined with a refractory ceramic mass or refractory monolithic mass 52. The tube 51 is provided with a side tube 53 similarly lined with a refractory mass 54 and containing an oil nozzle 55, the tube 51 leading into a reaction chamber 56 also having a similar refractory lining 57. In operation the gas and air admitted respectively through conduits 49 and are burnt in the burner 48 and the combustion gases are mixed in the tube 51 with hydrocarbon oil or gas admitted through the nozzle 55, the mixture being rapidly transferred to the reaction chamber 56.

As previously indicated the mixing apparatus of Fig. 3 may be substituted for the pipes 7 and 17 of the apparatus shown in Fig. 1. Likewise when conducting the process in an apparatus such as shown in Fig. 2 the mixing apparatus of Fig. 3 may be substituted for the pipes 45 and 46.

The use of the mixing apparatus of Fig. 3 has the advantage that it is made possible to bring about a very uniform and efficient mixing and diluting or dispersing of the carbonaceous material with a preheated gas or with products of combustion developed by burning a suitabie combustible gas injected through a burner into the mixing chamber. In this way a more rapid and uniform admixture of the carbonaceous material with the hotter gaseous material in the reaction chamber is brought about and the cosztuct time at the cracking temperature can be shortened.

The degree of the preheat imparted to the carbonaceous material that is to undergo cracking may be varied considerably while still preserving the advantages resulting from the preheating and premixing step. If a lower degree of preheat is imparted to the mixture of carbonaceous material and combustion gases or other preheated gaseous medium mixed therewith in the mixing apparatus, then a greater degree of preheat must be applied to the hotter gases that are brought to the reaction chamber to bring the temperature in the reaction chamber to a given crackz'ng temperature, and, vice versa, when a higher degree of preheat is imparted in the mixing chamber a lower degree of preheat may be given to the hotter gases that are brought to the reaction chamber. In other words, when employing the modification of the process wherein the pyrolizable carbonaceous material is preheated in a mixing apparatus such as shown in Fig. 3, the process is practiced with suitable regulation of'the temperature of thepreheated mixture and ofthe temperature of the'relwtively highly heated gaseous'flow through the reaction chamber so as to maintainthe temperature of the resulting mixture within the desired cracking range, preferably 800 to 1400" C. Higher temperatures within the limits of the capabilities of the available apparatus may be maintained in the reactionchamber. l preferto regulate the preheating of the gaseous medium (usually mainly a mixture of nitrogen and hydrogen) so as to bring the temperature thereof to at least 1700 C. at the point where its mixingwith the pyrolizable carbonaceous material begins to take place.

The following examples illustrate how the process of the invention may be carried into effect:

1. Tar oil containing 92% by weight of carbon and 6% by weight of hydrogen was cracked in the apparatus shown in Fig. 1 of the drawings. This composition is equivalent to 0.92 kgm. of carbonland 0.06 kgm. or 0.67 cubic metres of hydrogen per kgm. of material used. The reaction heat required to crack the material to carbon and hydrogen is 100 kgm. cals. per kgm. of oil. The specific heat of the tar oil was 0.55 kgm. cals. per kgm. at 1000 C. and the average temperature of the cracking reaction was 1000 C. The gases used for cracking were heated in the regcnerator 1 to a temperatureof 1700 C. The gases heated contained 40% by volume of hydrogen and 60% by volume of nitrogen and were supplied through conduit 30.

The following shows the heat required for cracking per kgm. of the tar oil:

Kgm. cals.

Reaction heat +100 Heat required to heat the tar oil 1000 C 550 Losses in the plant 10O -sso Heat available in the hot gases leavingthe regenerator at 1700 C.

Hz, O.40 1700 0.3301. 227 kgm. cals. N2, 0.60 l700 0.351 358 kgm. cals.

582 kgm. cals. per

cubic metre.

Heat in the gases leaving the reaction vessel at 1000" C.

Hz, 0.40X 1000x0317-.. 127 kgm. cals. N z, 0.60X 1000 X0334 200 kgm. cals.

327 kgms. cals. per cubic metre.

Therefore the heat available for cracking and heating the tar oil per cubic metre of gas is 582327=255 kgm. cals. per cubic metre Therefore the amount of gas required to crack 1 kgm. of the tar oil is cubic metres, or approximately 2.2 cubic metres.

The composition of the gases leaving thercaction zone is as follows:

Cubic metres H2 in the gases entering the reaction zone per kgm.

Therefore the-total amount of gases leavingthe reaction zone per kgm. of tar oil cracked is 2.87 cubic metres containing 54% by'volume of hydrogen and-46% by volume of nitrogen (neglecting the nitrogen in the tar oil and other impurities such as sulphur and neglecting the formation of methane).

A part of the gas obtained is recycled through lines 10 and 28 and'thc remainder is used for heating the rcgcncrator for the next cycle.

2. The process of Example 1 was modified by heating the gases in the regcnerator to a temperature of 1200 C. and further heating them to 1700 C. by supplying air through conduit 11 to burn 10% by volume ofthc gas which contained 54% by volume of hydrogen and 46% by volume of nitrogen.

Therefore, for each cubic metre of gas 0.1 cubic metre of hydrogen was burnt with approximately 0.27 cubic metre of air.

Thecomposition of the gas after combustion was 0.1 cubic metre of steam, 0.65 cubic metre of nitrogen and 0.44 cubic metre of hydrogen, or 1.19 cubic metres ob.- tained from 1 cubic metre of gas.

Thesensible heat at 1200 C. of the gas for the regenerator per cubic metre was:

Kgm. ca ls.

Hz, 0 .4 1200 0.32l 154 N2, 0.6X1200 D.340 245 The sensible hea-t'in 1.19 cubic metres of combustion gas at 1000 C. (temperature of reaction) Kgm. cals.

H2O, 0.1 X 1000 X0410 41 N2, 0.65X1000X0334 217 Hz; 0.44X1000' 0.317 139 The total heat in the gases used for the reaction per cubic metre of original gas is 399+0.1 2570= 399+ 257:656 kgm. cals.

The heat available for cracking per cubic metre of gas is 656.-397=259 kgm. cals., i. e., practically the same amount as in Example 1.

The composition of the gas entering the reaction zone after combustion (neglecting the steam formed) is as follows:

0.65 cubic metre of N2+0.44 cubic metre of Hz or approximately 40% Hz and 60% N2 by volume.

3. The same materials were used as in Examples 1 and 2 with the differences noted below but the process was carried out in the apparatus shown in Fig. 2.

The composition of the recycle gas was 45% Hz and 55% N2' by volume. The air and gas were heated to 350 C. The tar oil was pro-heated so that instead of 550kgm. cals. only 420 kgm. cals. per kgm. were required.

The gas was completely burned and the sensible heat obtained was. used to crack the tar oil but suppressing Reactions 2 to 7- hereinbefore referred to.

Theheat in the gases entering the reaction zone was as follows:

Kgm. cals. Potentialheat (45% Hz) per cubic metre 1155 Sensible heat of the air 1.08; 350 0.315 119 Sensible heat of the I gas 1 X 350 x0313 109 Heatin the gases leaving the reaction zone:

Kgtn. cals. H2O, 0.45- 1000 0.410 184 N2, 1000 0.334 466 Therefore the/heat available for cracking was 1-383- 650==733 kgm. cals. Therefore one cubic metre of recycle gas can be used to crack of tar oil.

The composition of the gas leaving the reaction zone (neglecting the steam) is:

1.4 cubic metre of N2+(l.74 0.l7) cubic metre of Hz=1.4 cubic metre of Nz+l.17 cubic metre of Hz: 2.62 cubic metres containing approximately 45.3% of H2 and 54.7% of N2 by volume or practically the same as the initial gas.

I claim:

1. The improvement in the manufacture of carbon black by thermal decomposition of hydrocarbons which comprises establishing a flow of a preheated mixture of hydrogen and nitrogen through an unobstructed reaction chamber, introducing air into said flow adjacent the entrance to said chamber in an amount sufiicient to burn a minor portion of the hydrogen content of said mixture, and so regulating the preheating of said mixture and the amount of air introduced for burning the hydrogen to bring the resulting mixture of nitrogen, hydrogen and steam to a temperature of at least 1700" C., introducing hydrocarbons into said flow at a point adjacent but downstream from the point of introduction of the air and thereby causing thermal cracking thereof to elemental carbon and hydrogen at a temperature in the range 8004400 C. and with a contact time of less than five seconds, and thereupon quickly cooling the decomposition products by introducing a cold mixture of nitrogen and hydrogen substantially free of oxides of carbon into the flow at a point adjacent but downstream from the point of introduction of said hydrocarbons to said flow.

2. The process for the manufacture of carbon black by thermal decomposition of hydrocarbons which comprises introducing a preheated gaseous fuel mixture of hydrogen and nitrogen substantially free of the oxides of carbon into an unobstructed reaction chamber, burning with air an amount of hydrogen contained in said gaseous fuel mixture sufiicient to bring the resulting gaseous combustion mixture containing nitrogen and steam to a temperature of at least 1700 C.; contacting hydrocarbons with said resulting combustion mixture to thermally decompose said hydrocarbons at a temperature in the range 800-1400 C. and at a contact time of less than five seconds with the resulting production of carbon and hydrogen from said hydrocarbons; quenching the resulting decomposition products mixture with a relatively cold gaseous mixture of nitrogen and hydrogen substantially free of the oxides of carbon, recovering carbon black from the resulting cooled mixture and recycling a portion of the remaining gaseous mixture containing nitrogen and hydrogen and substantially free of the oxides of carbon as said gaseous fuel mixture and recycling a portion of said remaining gaseous mixture as said relatively cold gaseous mixture.

3. The process according to claim 1 wherein the period during which the hydrocarbons are subjected to thermal cracking between 800--1400 C. is limited to not more than 0.5 second.

4. The process according to claim 2 wherein the period during which the hydrocarbons are subjected to thermal cracking between 800l400 C. is limited to not more than 0.5 second.

5. The improvement in the manufacture of carbon black by thermal decomposition of pyrolizable carbonaceous material which comprises establishing a relalively highly heated gaseous flow consisting at least mainly of nitrogen and hydrogen with any balance consisting substantially entirely of steam through an unobstructed reaction chamber, mixing a pyrolizable carbonaceous material with a hot gaseous medium to impart preheat thereto and rapidly introducing the preheated mixture thus formed into said relatively highly heated gaseous flow within said unobstructed reaction chamber, regulating the temperature of said preheated mixture and the temperature of said relatively highly heated gaseous flow so as to maintain the average temperature of the resulting admixture between 800 and 1700 C. and thereby causing thermal cracking of said pyrolizable carbonaceous material to form carbon black, cooling the products of the thermal cracking within a period of five seconds 10 below the thermal cracking temperature, and finally separating and recovering the carbon black produced.

6. A process according to claim 5 wherein the products of the thermal cracking step are cooled to below the thermal cracking temperature within a period of 0.5 second.

7. A process according to claim 5 wherein the gas s making up the relatively highly heated gaseous flow are substantially free of carbon oxides and wherein the period during which the pyrolizable material is subjected to thermal cracking between 800 and 1700 C. is limited to not more than five seconds and is varied inversely with the temperature maintained in the cracking zone.

8. A process according to claim 5 wherein the relatively highly heated gaseous flow contains a preponderating proportion of hydrogen.

9. A process according to claim 5 wherein the relatively highly heated gaseous flow contains a preponderating proportion of nitrogen.

10. The improvement in the manufacture of carbon black by thermal decomposition of pyrolizable carbonaceous material which comprises establishing a relatively highly heated gaseous flow consisting at least mainly of nitrogen and hydrogen with any balance consisting substantially entirely of steam through an unobstructed reaction chamber, mixing a pyroliznble carbonaceous material with hot combustion gases to impart preheat thereto and rapidly introducing the preheated mixture thus formed into said relatively highly heated gaseous flow within said unobstructed reaction chamber, regulating the temperature of said preheated mixture and the temperature of said relatively highly heated gaseous flow so as to maintain the average temperature of the resulting admixture between 800 and 1700 C. and thereby causing thermal cracking of said pyrolizable carbonaceous material to form carbon black, restricting the contact time at said temperature to less than five seconds and thereupon quickly cooling the decomposition products by introducing a cold mixture of nitrogen and hydrogen substantially free of oxides of carbon into the flow at a point downstream from the point of introduction of said pyrolizable carbonaceous material to said flow, and finally separating and recovering the carbon black produced.

11. The improvement in the manufacture of carbon black by thermal decomposition of pyrolizable carbonnceons material which comprises establishing a relatively highly heated gaseous flow consisting at least mainly of nitrogen and hydrogen with any balance consisting substantially entirely of steam through an unobstructed reaction chamber, mixing a pyrolizable carbonaceous material with hot combustion gases to impart preheat thereto and rapidly introducing the preheated mixture thus formed into said relatively highly heated gaseous flow within said unobstructed reaction chamber, regulating the temperature of said preheated mixture and the temperature of said relatively highly heated gaseous flowso as to maintain the average temperature of the resulting admixture between 800 and 1700 C. and thereby causing thermal cracking of said pyrolizable carbonaceous material to form carbon black, cooling the products of the thermal cracking within a period of 0.5 second to below the thermal cracking temperature by quenching said products with a relatively cold gaseous mixture of nitrogen and hydrogen substantially free of oxides of carbon, recover ing carbon black from the resulting cooled mixture and 1 1 rgcy c ling a portion of the remqining gaseous mixture con- 1,448,655 Darrak Mar. 13, 1923 tairiing'nitrogen andhjzdfoggn assaid gaseous flow and 1,669,618 Lewis May 15, 1928 recycling 'a portion of said femainjng gaseous mixture as 1,804,249 Day May 5, 1931 said relatively cold gaseous mixture; 1,987,643 Spear et a1. Jan. 15, 1935 I 6 2,106,137 Reed Jan. 18, 1938 References Cited in the file-of this patent or the 2,11 ,343 Reed May 10 193 original-patent 2,163,630 Reed June 27, 1939 UNITED STATES PATENTS 2,372,795 Kreici y 1945 2,37 ,796 Krejci May 15, 1945 1,364,273 Gerard at 41.1921 10 2 440 424 Wiegand et 1 API. 27 194 1;402,957 Poindexter Ian. 10, 1922 

